Designers' Corner

Acoustic metals

Noise can be reduced through the use of perforated metals as proven by their use in aircraft engines, office partitions, industrial equipment, HVAC, and ceiling panels to name a few. In such acoustical applications, perforated metals remove or reduce sound in one of two ways--as a facing for absorbent material, or as a part of a tuned resonant absorber that provides sound absorption in a targeted frequency range.

Telephone enclosures, for example, may use perforated metal as a protective or decorative covering for some special acoustical material that is either designed to absorb sound or to reflect or scatter sound in a special way.

For noise-control applications where the objective is to remove or reduce sounds that occur only in a narrow range of frequencies, perforated metals play an active role in sound absorption systems that are "tuned" to targeted frequencies. By employing such systems, designers can reduce the thickness of the absorbing layer and save space and cost. Such applications were developed by Theodore Schultz, Ph.D., and were validated by Riverbanks Acoustical Laboratories in tests sponsored by the Industrial Perforators Association.

The purpose of the perforated metal is to be so ‘transparent’ that the sound waves pass right through it, without being diminished or reflected.

Incident sound waves cause air to oscillate through the perforated metal sheet. Air mass in the holes and the springiness of the trapped air layer determine the preferred frequency of oscillation. At that frequency, the air moves in and out of the holes and, also back and forth in the sound absorptive layer where friction converts the acoustic energy into heat to remove it from the acoustical scene.

Peekaboo knob

The M1 push-to-close latch accommodates door misalignment in three planes and stores flush. In the closed position, the knob stores flush within the latch, reducing the chance of snagging clothing or running into the latch.

Interlocking serrations on both the pawl and the keeper accommodate grip variations. Spring-loaded, the pawl self-adjusts to variations in edge-distance from the keeper. Even when a cabinet door is only lightly or partially closed, the spring-loaded serrations engage, "grabbing" the door, holding it firmly in place. The latch and keeper design also accommodates misalignment laterally, along the frame edge.

The self-adjusting version has two available keepers.
One accommodates a flush door and frame configuration; the other is designed for
overlapping doors. A fixed grip style with a straight pawl is available for
perpendicular door/frame confi gurations or vertical installations.

To open, push the button to pop out the knob, turn to release the pawl, then, using the knob as a handle, pull the door open. To close, simply push the door shut. The door remains securely closed even if the knob is out. To store the knob flush, press it back into the housing.

It won't be too much longer and hardware design, as we used to know it, will be remembered alongside the slide rule and the Karnaugh map. You will need to move beyond those familiar bits and bytes into the new world of software centric design.

People who want to take advantage of solar energy in their homes no longer need to install a bolt-on solar-panel system atop their houses -- they can integrate solar-energy-harvesting shingles directing into an existing or new roof instead.

Kaspersky Labs indicated at its February meeting that cyber attacks are far more sophisticated than previous thought. It turns out even air-gapping (disconnecting computers from the Internet to protect against cyber intrusion) isn’t a foolproof way to avoid getting hacked. And Kaspersky implied the NSA is the smartest attacker.

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